This chocolate baklava is packed full of pistachios and bittersweet chocolate, then drizzled with a honey syrup to make wonderfully rich Greek dessert!
Preheat oven to 350F and move an oven rack to the middle position. Brush a 9x9 baking pan with a little butter.
Add the chocolate chips to the bowl of a food processor and pulse 3-4 times to break up the chocolate a little. Add the pistachios and pecans and pulse until finely chopped. Transfer the nuts and chocolate to a bowl and add the brown sugar, cinnamon, cardamom, and kosher salt. Stir to combine.
Unwrap the fillo and lay it out on a board. Cover the fillo with a damp dish towel. Layer 4 sheets of fillo in the baking pan, brushing each piece with butter as you layer. Since the pieces will be too long for the pan, fold the pieces over and turn the pan as you work so that you get an even coverage over the bottom.
Sprinkle 1/3 of the chocolate-nut mixture over the fillo. Layer 2-3 sheets over the chocolate-nut mixture; buttering, folding, and turning the pan you work. Repeat with 1/3 of the chocolate-nut mixture and 2-3 sheets of fillo. Then top with the last 1/3 and layer 4 sheets of fillo on top, buttering, folding the fillo, and turning the pan. Take one last sheet of fillo and cut it to length to just fit the baking pan. Butter the fillo and lay it carefully over the top.
Using a sharp knife, cut the baklava into 12 rectangles, making 4 cuts in one direction and 3 cuts in the other. (For smaller baklava, you can cut them all diagonally in half or take the side with 3 cuts and cut in between to make 24 small rectangles.)
Bake the baklava for 45 minutes, until golden.
Meanwhile, make the honey syrup. Add the water, sugar, honey, cinnamon, and salt to a saucepan and bring it to a boil. Let it boil for 5 minutes to completely dissolve the sugar, then take it off the heat. Taste the syrup and add more cinnamon and/or salt as needed.
Pour the hot syrup over the hot baklava once you take it out of the oven. Let the baklava cool to room temperature, about 4 hours.
If you want to make the chocolate syrup, combine the chocolate chips and butter in a heat proof bowl and put it over a pot of simmering water. Heat the chocolate until it is almost completely melted, then take it off the heat and stir until the chocolate is smooth. Drizzle the chocolate over the baklava.